Harry Potter actor Richard Griffiths dies at 65

British actor Richard Griffiths, best known for his roles in Harry Potter and the cult film Withnail & I, has died aged 65.

The portly star of stage and screen, one of Britain's best loved character actors, died on Thursday from complications following heart surgery, his agent Simon Beresford said.

Griffiths will be forever remembered by fans of cult classic Withnail & I as the amorous Uncle Monty, although he reached his biggest audience as Uncle Vernon Dursley in the Harry Potter films.

His roles also included a cookery-loving detective in the TV series Pie In The Sky.

Daniel Radcliffe, who played the boy wizard in the blockbuster Potter series, led the tributes to Griffiths who he said had offered him "encouragement, tutelage and humour".

"Richard was by my side during two of the most important moments of my career," Radcliffe said in a statement.

The first was in August 2000, when Radcliffe was filming his first ever shot as Harry. "I was nervous and he made me feel at ease," the actor recalled.

"Seven years later, we embarked on Equus together. It was my first time doing a play but, terrified as I was, his encouragement, tutelage and humour made it a joy," Radcliffe said.

"In fact, any room he walked into was made twice as funny and twice as clever just by his presence. I am proud to say I knew him."

Griffiths was born on July 31, 1947 in Yorkshire in northern England, the son of a steelworker.

His parents were both deaf so he had to learn sign language at an early age.

He left school at 15 but later went back into education to study drama, before joining the Royal Shakespeare Company.

Early film credits included Chariots of Fire, The French Lieutenant's Woman and Gandhi, before he landed a starring role in the 1987 comedy Withnail & I.

Griffiths played the predatory gay uncle of Withnail, an out-of-work, alcoholic actor played by Richard E Grant, in a film now regarded as a British classic.

Beresford said his client "brightened my days and enriched the life of anyone he came into contact with".

"Richard gave acting a good name. He was a remarkable man and one of our greatest and best-loved actors. He will be greatly missed," he said in a statement.

Nicholas Hytner, who directed Griffiths in one of his biggest hits in Britain, The History Boys, said he was "the life of every party".

Griffiths won several awards for his theatre role as an inspirational teacher in The History Boys in London and New York, and later won a Bafta nomination for his role in the film version.

"His performance in The History Boys was quite overwhelming: a masterpiece of wit, delicacy, mischief and desolation, often simultaneously," Hytner said.

"But that was just one small part of a career that spanned Shakespeare, cutting-edge new plays and major work in film and television."

The actor was awarded an OBE for services to drama in 2007.